Wireless communication systems have developed through various generations, including a first-generation analog wireless phone service (1G), a second-generation (2G) digital wireless phone service (including interim 2.5G and 2.75G networks) and third-generation (3G) and fourth-generation (4G) high speed data/Internet-capable wireless services. There are presently many different types of wireless communication systems in use, including Cellular and Personal Communications Service (PCS) systems. Example cellular systems include the cellular Analog Advanced Mobile Phone System (AMPS), digital cellular systems based on Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), the Global System for Mobile access (GSM) TDMA variation, and newer hybrid digital communication systems that use both TDMA and CDMA technologies. More recently, Long Term Evolution (LTE) has been developed as a wireless communications protocol for wireless communication of high-speed data for mobile phones and other data terminals. LTE is based on GSM, and includes contributions from various GSM-related protocols (e.g., Enhanced Data rates for GSM Evolution (EDGE)) and Universal Mobile Telecommunications System (UMTS) protocols (e.g., High-Speed Packet Access (HSPA)).
Accordingly, communications systems and devices are becoming increasingly diverse with new technological advancements. Many communications devices can now support various different communications technologies and protocols. Indeed, not only can various communications devices operate in a communications system (e.g., over a network infrastructure), many communications device may communicate with one another using direct device-to-device (D2D) communications when located in sufficient proximity to one another. For example, communications devices that support the Wi-Fi Direct standard may connect to each other via a D2D connection and communicate at typical Wi-Fi speeds with minimal setup and without requiring any intermediate wireless access point. Furthermore, the LTE Direct standard uses licensed spectrum and the LTE physical layer to provide a scalable and universal framework through which equipped communications devices can discover and connect to proximate peers and thereby establish D2D connections within ranges up to approximately 500 meters, whereas Wi-Fi direct tends to require the devices to be in closer proximity. Further still, wireless devices operating in the “Bluetooth” wireless communication spectrum can engage in D2D communication over relatively short distances, with an operating range ranging from a few meters to a few tens of meters, and near-field communication (NFC) technology refers to an open-platform, standard-based, short-range, high-frequency wireless communication technology that enables a bidirectional information exchange between NFC-equipped devices via magnetic field induction over very small distances (e.g., about ten centimeters). In any particular device, one or more D2D connections may be active at a given time, including at a time when the device may have a concurrent connection with one or more infrastructure elements (e.g., a WLAN access point, a cellular base station, etc.).
As such, D2D communications are becoming increasingly popular and multiple schemes already exist (with more continuing to emerge) because D2D communications can be faster, more efficient, more private, or otherwise advantageous to end users. Moreover, network operators and end users can realize substantial benefits from using D2D communications rather than communicating over a network infrastructure, especially when two or more devices seeking to communicate are located in proximity to one another and can establish a D2D connection with reasonably good quality. However, current D2D schemes typically select one technology (e.g., Wi-Fi Direct) that may be fastest or most ubiquitous. However, the default technology selection to use in a D2D connection may be unavailable or suboptimal under certain circumstances. For example, certain technologies may be incompatible across devices from different manufacturers, provide insufficient performance with respect to a particular communication session (e.g., a large file to be transferred), and/or cause coexistence issues in the devices that communicate over the D2D connection, including in-device and/or cross-device coexistence issues.
More particularly, as mentioned above, many wireless devices include multiple radios that each support a different radio access technology (RAT) that can be used to transmit and receive data. For example, the RATs that can be supported on a multi-radio device may include UMTS, GSM, CDMA2000, WiMAX, WLAN (e.g., Wi-Fi), LTE, and the like, and the multi-radio device may further have different radios that each support a different D2D RAT, which may include NFC, Bluetooth, Wi-Fi Direct, LTE Direct, and the like. Accordingly, an example multi-radio device may have multiple radios that operate simultaneously to provide various different functions. While the different radios may provide useful functionalities to a user, inclusion in a single device may give rise to in-device coexistence issues where one radio may interfere with another radio through radiative, conductive, resource collision, and/or other interference mechanisms. Furthermore, D2D communications may create cross-device coexistence issues through similar interference mechanisms due at least in part to the proximity between the devices communicating over the D2D connection. For example, the LTE uplink channel is adjacent to the industrial scientific and medical (ISM) band and may cause interference with Bluetooth and some wireless LAN (WLAN) channels that fall within the ISM band. In some instances, a Bluetooth error rate can become unacceptable when LTE is active in some channels within Band 7 or even Band 40 even though there may not be a significant degradation to LTE because simultaneous operation with Bluetooth can disrupt voice services terminating in a Bluetooth headset, which may be unacceptable to consumers.
Accordingly, solutions to select an optimal RAT to use in a D2D connection to mitigate coexistence issues and meet performance requirements are needed.